1. Field of the Invention
The present invention relates generally to methods and systems for determining the mass flow rate of a fluid, and more particularly to the operation of mass flow controllers.
2. Discussion of the Related Art
Many industrial processes require precise control of various process fluids. For example, in the semiconductor industries, mass flow meters (MFMs) are used to precisely measure the amount of a process fluid that is introduced to a process chamber. In addition to measuring the mass flow, mass flow controllers (MFCs) are used to precisely measure and control the amount of a process fluid that is introduced to a process chamber. It is to be understood that the term fluid as used herein applies to any type of gas or vapor to which controlled flow may be of interest.
Rate of decay (ROD) measurements can be used to calibrate a variety of flow measurement devices including mass flow controllers and mass flow meters. However, current rate of decay measurements may include a thermally induced error.
The disclosed embodiments include a system and method for improving the accuracy of a rate of decay measurement for real time correction in a mass flow controller or mass flow meter by using a thermal model to minimize thermally induced error in the rate of decay measurement.